Global studies of temperature trends in climate models and in observations have shown that natural climate variability (caused by changes in solar irradiance and by volcanic emissions) cannot explain the warming of the atmosphere over the past 100 years. Anthropogenic emissions of greenhouse gases and aerosols must be included in climate models to reproduce the observed warming, especially for the second half of the 20th century. But can regional climate change also be attributed to human activities?
Using the Hadley Centre climate model HadCM3, Stott has compared three ensembles of four simulations each with a record of near-surface air temperatures over land in six continental-scale regions. Each region is composed of subregions that capture local patterns of climate change but avoid the very small spatial scales that are not well represented in the model. Even though many uncertainties remain, the comparison indicates that for the past century, greenhouse gas emissions have caused increased warming in all six regions, whereas aerosol emissions have partly counteracted this trend. — JFU
Geophys. Res. Lett. 30, 10.1029/2003GL017324 (2003).